The first edition of The Reservoir Engineering Aspects of Waterflooding was published in 1970 and written by Forrest F. Craig, Jr. At the time of publication, much of the theory of oil displacement by water had been developed and many laboratory studies completed; however, the ability to perform computer modeling of 3D fluid flow in reservoirs with complex geologic depositions was in its infancy. In addition, several of the earliest, large-scale field applications of pattern waterflooding had begun, but long-term performance results were not yet known and various infill drilling programs had yet to be implemented. This second edition reviews the fundamentals of waterflooding theory and the experimental studies undertaken to understand the water displacement of oil in one, two, and three dimensions.